1. Field of the Invention:
This invention relates to a noise reduction means for use in a crawler tractor, and more particularly to a noise reduction means for use with a carrier roller in a crawler tractor for absorbing and shielding noise produced when a track link hits on the carrier roller.
2. Description of the Prior Art:
As is well known, track-type tractors and loaders produce metallic sounds of a considerably high level due to the hitting of the carrier roller by the track links of a track chain during operation. These sounds at the present time provide one of major noise sources which pose a public nuisance problem.
Heretofore, there have been proposed many attempts to avoid noises emanating from carrier rollers. For instance, one attempt in which a resilient material is directly bonded to the engaging surface of a carrier roller with a track link and one in which a resilient material or a cushion material is attached to the undersurface of the aforesaid engaging surface of a carrier roller by means of bolts and nuts.
The former attempt reduces noises to a large extent because the track link contacts a resilient material, providing a metal-to-resilient contact relation. Unfortunately, excessive wear of the resilient material or cushion material results due to a high load placed thereon by the track chain as well as a friction heat produced between the track chain and carrier roller.
In contrast thereto, the latter attempt provides a metal-to-metal contact relation and noises emanating from a carrier roller may be reduced to some extent. However, this attempt increases the manufacturing cost because of the complicated machining required. More particularly, it is a common practice to cast a carrier roller according to a split-casing technique wherein a roller is split into two halves with respect to its center plane and thereafter the aforesaid two halves are welded together into a form of a roller. As a result, the provision of a cushion material or a resilient material on the under surface of a carrier roller leads to a complicated casting process. In other words, the engaging surface of a roller with a track link should be cast separately, and a cushion member should be bolted to a body of the roller, thus resulting in tremendously complicated machining and casting processes.